1. Field of The Invention
This invention relates to diversity antenna systems. The background to the invention will be explained with reference to cellular mobile telephone systems, e.g. GSM. Other applications may occur readily to the reader.
2. Description of Related Art
Uplink communications are degraded by multipath propagation, interfering mobile stations using the same channel and by general noise. In order to reduce the effect of multipath propagation, diversity antennas have been proposed in which each antenna in an array has a respective branch tapped delay line in which the tap output signals are weighted and summed. The sums then need to be combined in a way that improves the signal to noise ratio. A conventional combining technique relies on estimation of the channel response and is referred to a maximal ratio combining. The impulse response measurements can be inaccurate leading to suboptimal combining.